These studies have demonstrated that, for benzo(j)fluoranthene, the likely route of activation is via the formation of a bay-region diol epoxide. Benzo (b) fluoranthene, as indicated by our studies, may be one of the first examples of an exception to this widely accepted theory of PAH carcinogenesis. Studies on the proximate mutagen of benzo(k)fluoranthene indicate that a dihydrodiol is formed in the "k-ring". Assays on this proximate will provide clear insight into the carcinogenic potential of benzo(k)fluoranthene. These studies will also provide essential data for determining the influence of environmental modifiers on the metabolic profiles of these benzofluoranthenes. Our tentative schedule for the 2nd year includes: a) structural characterization of the proximate mutagens of 2- and 3-methylfluoranthene formed in vitro, b) elucidation of the metabolites of dibenzo(c,g) carbazole in vitro, c) completion of all bioassays of benzofluoranthenes (synthetic metabolites) on mouse skin and new born mice, and d) bioassay of "synthetic metabolites" which are proximate mutagens of 2- and 3-methylfluoranthene on mouse skin for tumor initiation.